Re: [PATCH v7 0/8] Introduce 'yank' oob qmp command to recover from hanging qemu

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> On Thu, Aug 27, 2020 at 10:42:46AM +0200, Lukas Straub wrote:
> > On Tue, 18 Aug 2020 14:26:31 +0200
> > Lukas Straub <lukasstraub2@web.de> wrote:
> > 
> > > On Tue, 4 Aug 2020 10:11:22 +0200
> > > Lukas Straub <lukasstraub2@web.de> wrote:
> > > 
> > > > Hello Everyone,
> > > > In many cases, if qemu has a network connection (qmp, migration, chardev, etc.)
> > > > to some other server and that server dies or hangs, qemu hangs too.
> > > > These patches introduce the new 'yank' out-of-band qmp command to recover from
> > > > these kinds of hangs. The different subsystems register callbacks which get
> > > > executed with the yank command. For example the callback can shutdown() a
> > > > socket. This is intended for the colo use-case, but it can be used for other
> > > > things too of course.
> > > > 
> > > > Regards,
> > > > Lukas Straub
> > > > 
> > > > v7:
> > > >  -yank_register_instance now returns error via Error **errp instead of aborting
> > > >  -dropped "chardev/char.c: Check for duplicate id before  creating chardev"
> > > > 
> > > > v6:
> > > >  -add Reviewed-by and Acked-by tags
> > > >  -rebase on master
> > > >  -lots of changes in nbd due to rebase
> > > >  -only take maintainership of util/yank.c and include/qemu/yank.h (Daniel P. Berrangé)
> > > >  -fix a crash discovered by the newly added chardev test
> > > >  -fix the test itself
> > > > 
> > > > v5:
> > > >  -move yank.c to util/
> > > >  -move yank.h to include/qemu/
> > > >  -add license to yank.h
> > > >  -use const char*
> > > >  -nbd: use atomic_store_release and atomic_load_aqcuire
> > > >  -io-channel: ensure thread-safety and document it
> > > >  -add myself as maintainer for yank
> > > > 
> > > > v4:
> > > >  -fix build errors...
> > > > 
> > > > v3:
> > > >  -don't touch softmmu/vl.c, use __contructor__ attribute instead (Paolo Bonzini)
> > > >  -fix build errors
> > > >  -rewrite migration patch so it actually passes all tests
> > > > 
> > > > v2:
> > > >  -don't touch io/ code anymore
> > > >  -always register yank functions
> > > >  -'yank' now takes a list of instances to yank
> > > >  -'query-yank' returns a list of yankable instances
> > > > 
> > > > Lukas Straub (8):
> > > >   Introduce yank feature
> > > >   block/nbd.c: Add yank feature
> > > >   chardev/char-socket.c: Add yank feature
> > > >   migration: Add yank feature
> > > >   io/channel-tls.c: make qio_channel_tls_shutdown thread-safe
> > > >   io: Document thread-safety of qio_channel_shutdown
> > > >   MAINTAINERS: Add myself as maintainer for yank feature
> > > >   tests/test-char.c: Wait for the chardev to connect in
> > > >     char_socket_client_dupid_test
> > > > 
> > > >  MAINTAINERS                   |   6 ++
> > > >  block/nbd.c                   | 129 +++++++++++++++---------
> > > >  chardev/char-socket.c         |  31 ++++++
> > > >  include/io/channel.h          |   2 +
> > > >  include/qemu/yank.h           |  80 +++++++++++++++
> > > >  io/channel-tls.c              |   6 +-
> > > >  migration/channel.c           |  12 +++
> > > >  migration/migration.c         |  25 ++++-
> > > >  migration/multifd.c           |  10 ++
> > > >  migration/qemu-file-channel.c |   6 ++
> > > >  migration/savevm.c            |   6 ++
> > > >  qapi/misc.json                |  45 +++++++++
> > > >  tests/Makefile.include        |   2 +-
> > > >  tests/test-char.c             |   1 +
> > > >  util/Makefile.objs            |   1 +
> > > >  util/yank.c                   | 184 ++++++++++++++++++++++++++++++++++
> > > >  16 files changed, 493 insertions(+), 53 deletions(-)
> > > >  create mode 100644 include/qemu/yank.h
> > > >  create mode 100644 util/yank.c
> > > > 
> > > > --
> > > > 2.20.1  
> > > 
> > > Ping...
> > 
> > Ping 2...
> > 
> > Also, can the different subsystems have a look at this and give their ok?
> 
> We need ACKs from the NBD, migration and chardev maintainers, for the
> respective patches, then I think this series is ready for a pull request.

I'm happy from Migration:

Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> Once acks arrive, I'm happy to send a PULL unless someone else has a
> desire todo it.

Looks like Markus would like a QMP tweak; but other than that I'd also
be happy to take it via migration; whichever is easiest.

Dave

> 
> Regards,
> Daniel
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-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK